How Do Cells Keep Us Healthy?
Cell Membrane
The main function of a cell membrane is to determine what to let into the cell and what to let out.
The three ways molecules can get into a cell is by some form of diffusion, by cell signaling, or by both.
The phospholipid bilayer serves as a semi permeable barrier; it is the main component of the membrane
The size and polarity of a molecule determines if they can enter or exit the cell
- This a layer of phosphates and lipids
- The tails of a phospholipid are hydrophobic and they are attracted to each other, facing inward.
- The heads of a phospholipid are hydrophilic and they are attracted to water, facing outward.
- Cholesterol is utilized to keep the tails from tangling and to stabilize the membrane
- Glycoprotein and glycolipids receive and transmit signals to other cells
- Peripheral proteins let the molecule through the membrane halfway
Transport
Active Transport
Passive Transport
Moving substances from a low concentration to a high concentration
Against the concentration gradient
Energy is needed for this (ATP used)
Transport Protein is used
Moving substances from a high concentration to a low concentration
Along the concentration gradient
There is no energy needed for this (No ATP)
Two Types: Simple Diffusion and Facilitated Diffusion
Simple Diffusion: Does not require
Facilitated Diffusion: Using a channel protein
Osmosis
Nonpolar and small
moves through the cell membrane easily,
O2 and CO2
Uses a channel protein to move through the cell membrane
Large and polar
Glucose, ions
Osmosis is defined as the movement of water either into or out of a cell.
Isotonic
Hypertonic
Hypotonic
- The rate of water molecules moving into the cells is greater than water moving out of cells
- The plant cell swells and the animal cell can burst
- Plant Cell: Turgid, Animal Cell: Lysed
- Turgor Pressure
- The rate of water molecules moving into the cells is less than water moving out of cells
- The plant cell shrinks and the animal cell shrivels up
- Plant Cell: Plasmolysed, Animal Cell: Crenated
- The rate of water molecules moving into the cells is the same as the water moving out of cells
- The plant cell and animal cells exhibit little to no difference
- Plant Cell: Normal, Animal Cell: Normal
Endocytosis
Exocytosis
Sodium Potassium Pump
Active transport (moving against the concentration gradient)
Transports three Na+ to the outside of the cell for the transport of every two K+ ions to the inside
Endocytosis engulfs large particles too large to come in through regular transport using vesicle transport
Endocytosis requires a cell receptor (glycolipid/glycoprotein)
Viruses can move in by imitating a human cell and binding to the receptor
Exocytosis occurs when cells want to get rid/release something.
Exocytosis also requires a glycoprotein/glycolipid as a signal to get out of the cell
Viruses can exit the cell after replicating through exocytosis
Type 2 Diabetes
Type 1 Diabetes
Autoimmune distance: immune system attacks pancreas cells that produce insulin
Without insulin, glucose doesn’t get into the cells and accumulates in the blood
Treatment: Insulin injections, food choices, physical activity, controlled blood pressure and cholesterol
Insulin levels low, glucose levels high
Without the proper signals, glucose cannot get into the cells and accumulates in the blood
Insulin levels high, glucose levels high
Produce insulin but the receptors on the cells don’t bind or respond to the binding
Treatment: Medicines to reduce blood sugar, food choices, exercise, controlled BP and cholesterol